1. Field of the Invention
The present invention relates to an optical plate and a backlight module using the same and, particularly, to an optical plate and a backlight module using the same employed in a liquid crystal display.
2. Description of the Related Art
Referring to FIGS. 4 and 5, a typical direct type backlight module 100 includes a frame 11, a plurality of light sources 12, a light diffusion plate 13, and a prism sheet 10 The light sources 12 are disposed in an inner side of the frame 11. The light diffusion plate 13 and the optical plate 10 are disposed on the light sources 12 above a top of the frame 11 in that order. The light diffusion plate 13 includes a plurality of diffusing particles (not shown) configured for diffusing light. The optical plate 10 includes a transparent substrate 101 and a prism layer 103 formed on a surface of the transparent substrate 101. The prism layer 103 forms a plurality of elongated V-shaped protrusions 105.
In use, light from the light sources 12 enters the diffusion plate 13 and becomes scattered. The scattered light leaves the diffusion plate 13 to the prism sheet 10. The scattered light then travels through the optical plate 10 and is refracted out at the elongated V-shaped protrusions 105 of the prism sheet 10 Thus, the refracted light leaving the optical plate 10 is concentrated at the prism layer 102 and increases the brightness (illumination) of the prism sheet 10 The refracted light then propagates into a liquid crystal display panel (not shown) disposed above the prism sheet 10
However, although light from the light sources 12 enters the diffusion plate 13 and becomes scattered, after light leaving the optical plate 10, light spot of the light sources 12 often occurs.
In order to reduce or eliminate the light spot of the light sources 12, the backlight module 100 should further include an upper light diffusion film 14 disposed on the prism sheet 10 However, although the upper light diffusion film 14 and the optical plate 10 are in contact with each other, a plurality of air pockets still exist at the boundary between the light diffusion film 14 and the prism sheet 10 When the liquid crystal display device 100 is in use, light passes through the air pockets, and some of the light undergoes total reflection at one or another of the corresponding boundaries. In addition, the upper light diffusion film 14 may absorb an amount of the light from the prism sheet 10. As a result, the brightness of light illumination of the liquid crystal display device 100 is reduced.
Therefore, a new optical plate is desired in order to overcome the above-described shortcomings.